Delayed action switch



May 22, 1962 E. D. LIVENICK DELAYED ACTION SWITCH 2 Sheets-Sheet 1 Filed 00*. 31, 1960 A an .T L a a 5 I\J 6 J 1 m. m w 3 In fl- Q In 1% Mr 1% w M W n WUQ w l 6 m A F c FIG. 3

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INVENTOR.

EDWARD D. LIVENICK ATTORNEY FIG.4

May 22, 1962 E. p. LIVENICK 3,036,230

DELAYED ACTION SWITCH Filed Oct. 31, 1960 2 Sheets-Sheet 2 MIC. Juo

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1 aunssaad smavds mvmoo mvmoa United States Patent 3,036,230 DELAYED ACTIGN SWITCH Edward D. Livenick, 59086 Clover Road, Mishawaka, Ind. Filed Oct. 31, 196i), Ser. No. 66,388 8 Claims. (Cl. fill-141.3)

The present invention relates to a switching device, and more particularly to a delayed action electrical switching device.

Conventional delayed action electrical switches and relays of the hot wire type are subject to variations in the length of the time delay, due to variations in the temperature of their surroundings before and during the operation of the switch and to variations of the operating voltage. Furthermore, the conventional switches are often made non-operating by extremes of heat and cold, for example in deserts or in the arctic. Also, minor changes in the positions of the components, due to such factors as warping of the mount, often seriously change the operating characteristics of the switch or render it inoperable altogether. Therefore, it is a principal object of the present invention to provide a delayed action switching device which compensates for variations in the temperature of its surroundings and for variations in its operating voltage, and which will adjust itself to minor warping of its base.

In some applications it may be desired to interrupt the time delay and open the circuit before the mechanism ordinarily would. It is therefore an additional object of the invention to provide a delayed action device which can be interrupted in its operation at any part of the delay period, and which will open quickly either at the end of the delay period or upon interruption.

An additional object of the present invention is to provide an ambient temperature compensated delayed action device which will close rapidly when actuated and open rapidly at the end of the delay period, and in which the entire delay period starts when the actuating switch is released.

A further object of the invention is to provide a delayed action switch which requires very little power and which is adjustable in manufacture from a short delay period to one which is considerably longer than that attainable with conventional hot-wire delayed action switches.

Conventional switches which provide quick relay action use costly electromagnetic relays and other complex equipment. Furthermore, if a time delay action is desired in the relay action, a separate time delay element must be connected into the circuit, requiring still more expensive and sometimes bulky units. It is therefore another object of the invention to provide an integral relay and time delay which is simple in construction and quick in opening and closing.

Still another object is to provide a delayed action switch which can be manufactured easily and inexpensively from readily available materials and which requires little or no servicing over a long period of use.

An additional object of the invention is to provide an ambient temperature and voltage compensated delayed action device which is rugged and independent of any normal variations in its environment, including its orientation with respect to the earths surface, the temperature, humidity, air pressure and the like.

Additional objects and advantages will become apparent from the following description and accompanying drawings, wherein:

FIGURE 1 is a schematic view of the delayed action switch;

FIGURE 2 is a schematic view of the portion of the switch in operation immediately after the actuating switch has been closed;

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FIGURE 3 is a schematic view of the portion of the switch in operation during the delay period after the actuating switch has been opened again;

FJGURE 4 is a schematic view of the portion of the switch in operation after the switch to interrupt the delay period has been closed;

FIGURE 5 is a graph showing the action of a portion of the switch after it has been energized;

FIGURE 6 is a graph showing the action of the switch after another portion is energized;

FIGURE 7 is a graph showing the action of the switch after still another portion has been energized; and

FIGURE 8 is a graph showing the action of the switch after two portions have been energized.

Referring to the drawings, and to FIGURE 1 in particular, numeral 10 designates a load, such as a light or motor, powered by a supply voltage having a positive side 12 and a negative side 14. Connected between the load and the negative side 14 is an operating switch 16 which may be of any desired normally open type. Connected to terminal 18 of switch 16 is lead 20 which carries current to a conducting contact arm 22 pivoted at 24 to swing freely therearound. At a distance L from pivot point 24, actuating wire 30 is connected to contact arm 22, one end of a spring 32 is connected on the opposite side of the arm, and the other end is held fixed in order that the spring will urge arm 22 to the right as seen in FIGURE 1 around pivot 24. Actuating wire 30 is connected tautly at its other end to one end of a bimetal element 34 to resist the movement of arm 22. The opposite end of element 34 is mounted rigidly to the base 35 and joins a conductor 36 which carries current from there to the positive side 12 of the voltage source, as emphasized in heavy lines in FIGURE 2. Element 34, which is merely one type of a number of suitable thermoresponsive means, deflects to the right as viewed in FIG- URE 1 as the temperature rises, in the well known manner, and for convenience of description element 34 will be referred to as a thermostat or thermostatic means.

Connected to the fundamental circuit of the load, power source and switch is the time delay circuit, consisting of contact 50 on arm 22, and arm 52 pivoted at 54 and carrying contact 56, said contact being adapted to engage contact 50 and close the circuit between the two arms 22 and 52. The holding circuit, emphasized in FIGURE 3, includes a lead 58 connected to pivot point 54 at one end and to a heating element 60 at the other end, the heating element being connected to the negative side 14 by lead 62. Thermostat 63, consisting of a thermoresponsive bimetallic element identical or similar to element 34, responds to heating element 60, moving actuating wire 64 to the right as shown in FIGURE 1, causing contacts 50 and 56 to open under the influence of spring 66 urging arm 52 in the direction to separate said contacts. It is thus seen that by this circuitry, contacts 50 and 56 are initially closed upon the closing of switch 16, completing the circuit through lead 20 and wire 30, thermostat 34, and leads 3-6 and 12. Thermostat 34 is responsive to ambient temperature and compensates for variations in said temperature in order to eliminate this factor from the operation of the circuitry. As heating element 60 heats thermostat 63 after contacts 50' and 56 have been closed in the foregoing manner, the thermostat gradually swings to the right, as viewed in FIGURE 1, until arm 52 has moved sufliciently to separate contacts 50 and 56, thus breaking the circuit after the desired time delay in the operation of the present device.

In the event it is necessary to interrupt the delayed action of the present device, a circuit integrated with the holding circuit is incorporated therein, as emphasized in FIGURE 4, consisting of a post 70 connected to lead 62, a post 72, lead 74 connecting the latter post with base 68 of thermostat 63, and actuating wire 64 between thermostat 63 and arm 52. The two posts are operatively connected by switch element 76, forming with said posts a push button switch. When it is desired to interrupt the operation of the delayed action holding circuit, switch e1ement76 is pressed into contact with posts 70 and 72, thereby closing the circuit through lead 74, thermostat 63 and actuating wire 64. The current passing through wire 64 causes the wire to expand in length, permitting spring '66 to move arm 52 to the right sufiiciently to separate contacts 50 and 56, thus opening the circuit through the load 10.

In the operation of the present delayed action device, with closing of operating switch 16 a current flows through lead 12, load 10, lead 20 and actuating wire 3% which is thereby heated and increased in length by the flow of current therethrough. As a result of this expansion, the arm 22 moves angularly through a small arc around its pivot24 and moves contact 50 against contact 56, the wire functioning as illustrated in FIGURE 5. This creates a current path through contact arm 22, contact 50-, contact 56, contact arm 52 and low resistance heater 60 in such a manner that the full supply voltage, minus a small voltage drop across low resistance heater 60, is still applied to load 10 and actuating wire 30 after the operating switch 16 is opened.

Upon opening of operating switch 16, the load current through low resistance heater 60 causes the bimetal delay thermostatic element 6 3 to be heated at a slow rate. As the temperature of bimetal element 63 rises, it bends, permitting wire 64 to move lengthwise to the right, as seen in FIGURE 3 and in the manner illustrated in FIG- URE 7. This causes contact arm 52 to move angularly through a small are around its pivot point 54 in such a manner that first the slack is taken up on actuating wire 30 followed by a minute separation of contacts and 56.

This minute separation of contacts 50 and 56 results in a slight reduction of current through load and actuating wiredue to contact resistance. This further results in a temperature reduction of actuating wire 30, whereupon it immediately starts to contract in length, causing a still greater separation of contacts and 56 and an additional increase of contact resistance. This cycle is highly regenerative and results in a fast contact separation upon the first appearance of any increase in contact resistance, principally occurring at the'endof the delay period when the heated actuating wire 30 is being held taut by the flexure of time delay bimetal element 34-. At no other time will an increase in contact resistance cause an opening of contacts 50 and 56.

Separation of contacts 50 and 56 causes the current to I be reduced to Zero through load 10, actuating wire 30 and heating element 60, whereupon actuating wire 30 completely contracts to its previous length, returning contact arm 22 to its original position. Also, bimetal element 63 cools and returns to its original position. This completes the fast closing-delay before opening cycle of the relay.

If it is desired to open the relay contacts at any time during the delay period, the action is the same as described above, up to and including the delay period, as illustrated in FIGURE 8. Closing of operating switch 76 causes a current to flow through actuating wire 64, heating the actuatingwire and resulting in an increase in length of the wire from expansion, as illustrated in FIG- URE 6. An increase in length of wire 64 causescontact arm 52 to move in a small arc around its pivot point 54, causing contact 56 to move away from contact 50. Separation of contacts 50 and56 causes the current to be reduced to zero through load It actuating wire 30 and heater 60, whereupon actuating wire 30 contracts to its previous length, returning contact arm 22 to its original position, and bimetal element 63' cools and returns to its original position. When operating switch 76 is opened,

the current fiowingthrough actuating wire 64 is reduced to zero, causing the actuating wire to contract to its original length and contact arm 52 to return to its original position, thus completing the fast closing-partial delay before opening cycle of the relay.

Proper contact spacing over any ambient temperature range is maintained by the symmetrical bridge type configuration of the thermal and mechanical elements. Ac-

tuating wires 3d and are identical in material, diameter and length; therefore, they will both change length in exactly the same proportion during any change in ambient temperature, thus maintaining exactly the original contact spacing. Bimetal element 34 effectively and accurately counteracts any change in spacing of contacts 50 and 56 resulting from flexure of bimetal element 63 in response to ambient temperature changes.

Uniform balanced travel ofcont'acts 50 and 56 is maintained during normal supply Voltage variations by the symmetrical bridge configuration of electrical and thermal elements. Actuating wires 30 and 64, being identical in material, diameter, length and electrical characteristics, and being supplied from the same source of voltage, will change in length in exactly the same proportion during any change in supply voltage. Thus the travel of contact 50 is exactly proportional to the travel of contact 56 and in the same direction. Constant delay time is maintained during normal supply voltage variations by virtue of the fact that heating element 60 and actuating wire 34) are supplied by the same source of voltage. A fractional change of supply voltage will appear across both heating element 64} and actuating wire 30. Therefore, the ratio of power loss in heating element 6t} to the power loss in actuating wire 30 and hence the ratio of flexure of bimetal element 63 to expansion of actuating wire 3%) will remain constant.

One application of this invention is in the operation of automobile interior lights, which are normally switched on and off by a momentary contact door switch. It is desirable for the interior lights to stay on for a period of time after the door is closed so that the operator may see his instrument panel controls prior to they time he is ready to start the engine and drive away. It is also desirable that the interior lights go off immediately upon the starting of the engine. This same application has further merit when an automobile operator leaves the car in a darkened garage or parking area. The present time delay device enables the garage or parking area to be sufiiciently illuminated by the car interior lights to permit the car occupants to leave the otherwise darkened area safely and easily.

While only one embodiment of my delayed action switch has been described in detail herein, various changes and modifications may be made without departing. from the scope of the present invention.

I claim: I

l. A delayed action electrical switching device, comprising a positive lead and a negative lead for connection with a load, a push button switch in one of said leads, a circuit connected between said leads and between said switch and the load in said one lead, two relatively movable pivoted arms, an electrical contact mounted on each of said arms, springs operatiyelyconnected'to each of said arms for moving said contacts in the same direction, a thermo-expansible wire in said circuit connected to one of said arms for closing said contacts with an in crease in temperature, a thermostatic means supporting one end of said wirefor compensating for changes in ambient temperature, a thermo-expansible wire of the same size and character as said first mentioned element connected to the other of said arms for opening said contacts with an increase in temperature, a thermostatic means supporting one end of said second mentioned wire, a heating element adjacent said last mentioned thermostatic means for moving said last mentioned thermoexpansible wire in the direction to separate said contacts, a lead connecting said last mentioned arm with said resistance element, a lead connecting one of said first mentioned leads with said last mentioned thermo-expansible wire for causing said contacts to separate when a current is passed through said last mentioned wire, and a push button switch in said last mentioned lead.

2. A delayed action electrical switching device, comprising two leads for connection with a load, a manually operated switch in one of said leads, a circuit connected between said leads and between said switch and the load in said one lead, two relatively movable pivoted members, an electrical contact mounted on each of said members, resilient means operatively connected to each of said members for moving said contacts in the same direction, a thermo-expansible wire in said circuit connected to one of said members for closing said contacts with an increase in temperature, a thermostatic means supporting one end of said wire for compensating for changes in ambient temperature, a thermo-expansible wire of the same size and character as said first mentioned element connected to the other of said members for opening said contacts with an increase in temperature, a thermostatic means supporting one end of said second mentioned wire, an electrical resistance element for heating said last mentioned thermostatic means for moving said last mentioned thermo-expansible wire in the direction to separate said contacts, a lead connecting said last mentioned member with said resistance element, a lead connecting one of said first mentioned leads with said last mentioned thermo-expansible wire for causing said contacts to separate when a current is passed through said last mentioned wire, and a manually operated switch in said last mentioned lead.

3. A delayed action electrical switching device, comprising two leads for connection with a load, a switch in one of said leads, a circuit connected between said leads and between said switch and the load in said one lead, two relatively movable members, an electrical contact mounted on each of said members, resilient means operatively connected to each of said members for moving said contacts in the same direction, a thermo-expansible element in said circuit connected to one of said members for closing said contacts with an increase in temperature, a thermostatic means connected to one end of said element for compensating for changes in ambient temperature, a thermo-expansible element connected to the other of said members for opening said contacts with an increase in temperature, a thermostatic means connected to said second mentioned element, an electrical resistance element for heating said last mentioned thermostatic means for moving said last mentioned thermoexpansi-ble element in the direction to separate said contacts, a lead connecting said last mentioned member with said resistance element, a lead connecting one of said first mentioned leads with said last mentioned thermoexpansible element for causing said contacts to separate when a current is passed through said last mentioned element, and a switch in said last mentioned lead.

4. A delayed action electrical switching device, comprising two leads for connection with a load, a switch in one of said leads, a circuit connected between said leads and between said switch and the load in said one lead, two relatively movable members, an electrical contact mounted on each of said members, resilient means operatively connected to each of said members for moving said contacts in the same direction, a thermo-expansible element in said circuit connected to one of said members for closing said contacts with an increase in temperature, a thermostatic means connected to one end of said element for compensating for changes in ambient temperature, a thermoexpansible element connected to the other of said members for opening said contacts with an increase in temperature, a thermostatic means connected to said second mentioned element, an electrical resistance element for heating said last mentioned thermostatic means for moving said last mentioned thermo-expansible element in the direction to separate said contacts, a lead connecting said last mentioned member with said resistance element, and means for interrupting the current through the leads to the load.

5. A delayed action electrical switching device, comprising two leads for connection with a load, a switch in one of said leads, a circuit connected between said leads and between said switch and the load in said one lead, two relatively movable members, an electrical contact mounted on each of said members, resilient means operatively connected to each of said members for moving said contacts in the same direction, a thermo-expansible element in said circuit connected to one of said members for closing said contacts with an increase in temperature, a thermostatic means connected to one end of said element for compensating for changes in ambient temperature, a thermostatic means connected to the other of said members, an electrical resistance element for heating said last mentioned thermostatic means for moving said last mentioned member in the direction to separate said contacts, and a lead connecting said last mentioned member with said resistance element.

6. A delayed action electrical switching device, comprising two leads for connection with a load, a switch in one of said leads, a circuit connected between said leads and between said switch and the load in said one lead, two relatively movable members, an electrical contact mounted on each of said members, resilient means operatively connected to each of said members for moving said contacts in the same direction, a thermo-expansible element in said circuit connected to one of said members for closing said contacts with an increase in temperature, a thermostatic means connected to said element for compensating for changes in ambient temperature, a thermostatic means connected to the other of said members, an electric-a1 resistance element for heating said last mentioned thermostatic means for moving said last mentioned member in the direction to separate said contacts, and a lead connecting said last men-tioned member with said resistance element.

7. A delayed action switch, comprising two leads for connection with a load, a switch in one of said leads, a circuit connected between said leads and between said switch and the load in said one lead, two relatively movable members, an electrical contact mounted on each of said members, a thermo-expansible element in said circuit connected to one of said members for closing said contacts with an increase in temperature, a thermostatic means connected to said element for compensating for changes in ambient temperature, a thermostatic means connected to the other of said members, and an electrical resistance element for heating said last mentioned thermostatic means for moving said last mentioned memher in the direction to separate said contacts.

8. A delayed action switch, comprising two leads for connection with a load, a switch in one of said leads, a circuit connected between said leads and between said switch and the load in said one lead, two relatively movable members, an electrical contact mounted on each of said members, a thermo-expansible element in said circuit connected to one of said members for closing said contacts with an increase in temperature, a thermostatic means connected to the other of said members, and an electrical resistance element for heating said thermostatic means for moving said last mentioned member in the direction to separate said contacts.

No references cited. 

